Conventional methods for detecting the wear status of a conveyor belt or a feed belt have been such that, as shown in FIGS. 8A and 8B, a rubber magnet 51, which is magnetized in the thickness direction of a conveyor belt 50, is embedded between the surface 50a of a rubber member 50A of a conveyor belt 50 and a reinforcement member 50B provided on the rear surface 50b side of the conveyor belt 50, and also a magnetic sensor 52, which detects changes in the magnetic field from the rubber magnet 51, is disposed in a location where the rubber magnet 51 passes by. And the depth of wear of the conveyor belt 50 is calculated from the magnitude of magnetic field detected by this arrangement. Also, as shown in FIG. 8C, a belt deviation detecting means 54 is disposed in a position lateral to a pulley 53 around which the conveyor belt 50 is wrapped, and thus the amount of deviation of the conveyor belt 50 is measured using a noncontact distance sensor such as an ultrasonic sensor. Then the depth of wear of the conveyor belt 50, or the thickness of the worn belt, is calculated with accuracy by correcting the calculated depth of wear of the conveyor belt 50 for the amount of belt deviation measured as described above. See Reference 1, for example.
Also, the conveyor belt 50 is most susceptible to wear in the middle portion of the belt width where the loads are placed. Therefore, as the wear progresses, the thickness of the belt will have a distribution (unevenness) in the belt width direction. Thus, in order to measure the distribution of belt thickness in the width direction of the conveyor belt 50, the rubber magnets 51 are disposed over the entire width of the conveyor belt 50, and at the same time a plurality of the magnetic sensors 52 are arranged at predetermined intervals in the belt width direction as shown in FIGS. 9A and 9B.
Reference 1: Japanese Unexamined Patent Application Publication No. 2007-284150